1. Field of the Invention
The present invention relates in general to a drive unit for a vehicle having a transversely-mounted engine or a four-wheel-drive vehicle, and more particularly to techniques for reducing an axial dimension of such a drive unit.
2. Discussion of Related Art
In one known type of vehicle, a differential gear device and a transfer device are disposed on one radial side of an input shaft of a transmission that is coaxial with a crankshaft of an engine, for example, on one of front and rear sides of the input shaft where the engine is transversely mounted. In this type of vehicle, the engine and a transaxle fixed to the engine are elastically supported by the body of the vehicle through engine mounts, but the weight distribution about the crankshaft is not uniform or even, so that the vehicle is relatively likely to generate vibration and noises, giving rise to a problem of deterioration of so-called “noise and vibration performance”.
To solve this problem, JP-3-284427A proposes a four-wheel-drive vehicle drive unit in which a differential gear device is disposed on a front side of an engine, while a transfer device (power distributing mechanism) is disposed on a rear side of the engine, so that the weight distribution about the crankshaft is made even.
The conventional four-wheel-drive vehicle drive unit described above includes a first intermediate drive gear which receives a drive force for driving the differential gear device and which is fixed to the output shaft of a transmission. The drive unit further includes a transfer drive gear which receives a drive force for driving the transfer device and which is also fixed to the output shaft of the transmission such that the transfer drive gear and the first intermediate gear are parallel to each other. Accordingly, this drive unit has a first power transmitting path for driving the differential gear device and a second power transmitting path for driving the transfer device, which are operatively connected to the output shaft of the transmission, so that the drive unit has a relatively large size. In this respect, there has been a need of reducing the size of the drive unit. It is also noted that the input shaft and output shaft of the transmission are coaxial with the crankshaft in the above-described conventional four-wheel-drive drive unit. This means that the solution proposed by JP-3-284427A is not applicable to a drive unit including a manual transmission, typically of a parallel two-axes type, for example.